<h2>semaphore_wait</h2>
<hr>
<p>
<strong>Function</strong> - Wait on the specified semaphore.
<h3>SYNOPSIS</h3>
<pre>
<strong>kern_return_t   semaphore_wait</strong>
                <strong>(semaphore_t</strong>                          <var>semaphore</var><strong>);</strong>
</pre>
<h3>PARAMETERS</h3>
<dl>
<p>
<dt> <var>semaphore</var>
<dd>
[in send right] The port naming the semaphore that the wait operation is being performed upon.
</dl>
<h3>DESCRIPTION</h3>
<p>
The <strong>semaphore_wait</strong> function decrements the semaphore count. If the
semaphore count is negative after decrementing, the calling thread
blocks.  Device driver interrupt service routines (ISR) should never
execute <strong>semaphore_wait</strong>, since waiting on a semaphore at the ISR level
may, and often will, lead to a deadlock.
<h3>RETURN VALUES</h3>
<dl>
<p>
<dt> <strong>KERN_INVALID_ARGUMENT</strong>
<dd>
The specified semaphore is invalid.
<p>
<dt> <strong>KERN_TERMINATED</strong>
<dd>
The specified semaphore has been destroyed.
<p>
<dt> <strong>KERN_ABORTED</strong>
<dd>
The caller was blocked due to a negative count on the semaphore, and was
     awoken for a reason not related to the semaphore subsystem
     (e.g. <strong>thread_terminate</strong>).
<p>
<dt> <strong>KERN_SUCCESS</strong>
<dd>
The semaphore wait operation was successful.
</dl>
<h3>RELATED INFORMATION</h3>
<p>
Functions:
<a href="semaphore_create.html"><strong>semaphore_create</strong></a>,
<a href="semaphore_destroy.html"><strong>semaphore_destroy</strong></a>,
<a href="semaphore_signal.html"><strong>semaphore_signal</strong></a>,
<a href="semaphore_signal_all.html"><strong>semaphore_signal_all</strong></a>,
<a href="device_get_status.html"><strong>device_get_status</strong></a>.
